Defect inspection plays a key role in yield management of semiconductor wafer processing for integrated circuit (IC) manufacturing. This may similarly be the case for other fabricated components. Identifying if there is a defect is based on wafer images obtained from optics systems.
Currently, defects in fabricated components (e.g. wafers) can be detected by comparing a target component (e.g. portion of a target die) of a fabricated device to reference components (e.g. corresponding portions of other reference dies) of the fabricated device, since oftentimes wafers are configured with repeating dies (i.e. having repeating patterns across the dies) at least in a same vicinity. For example, the reference dies may be adjacent, or otherwise closest in vicinity to, the target die. In general inspection systems accomplish this by taking images of the target and reference components for comparison purposes. For example, a laser scanner will scan a line of the wafer across a plurality of the dies to collect an image for that line. The inspection system will then take a piece of the image for a corresponding part of each of the target and reference dies.
Defects are then detected by performing two separate comparisons using the images to generate two separate results, one comparison being between the target component and one of the reference components and another comparison being between the target component and the other one of the reference components. A value combining those comparison results is generally used as a signal of a defect in the target component. This is often referred to as double detection.
Unfortunately, however, the target and reference component images include significant noise from systems and processes. This noise issue is one of the major problems for limiting sensitivity of the inspection system. Therefore, extracting noise statistics is critical for inspection algorithms. Existing inspection algorithms collect noise statistics across an entire region (care area groups). However, more and more inspection tools are adopted in logic regions with the design rule shrinking. Usually logic regions are so complicated in terms of design pattern that statistics for the entire region are not representative enough for a particular local area with a possible defect. This will limit inspection algorithm sensitivity.
There is thus a need for addressing these and/or other issues associated with the prior art techniques used for defect detection in fabricated components.